The present invention relates generally to a remote control system for controlling operation of two or more electrical appliances, and is particularly concerned with the control of a combination ceiling fan and light assembly.
It is common, particularly in relatively hot climates, for some or all of the rooms of a building to have the normal ceiling light fixture replaced with a combination ceiling fan and light assembly. During daylight hours the fan may be operated alone, while at night the light may be operated alone or in combination with the fan.
There are a number of problems associated with installation and control of a combination ceiling fan and light assembly, which prior art systems have attempted to overcome. The conventional house lighting circuit is a two wire circuit, and considerable expense is involved if any modification to this circuit is required for installation of a combination fan and light. If modification to the circuit is to be avoided, the fan and light control must be installable either at the location of the wall light switch or at the overhead ceiling fan and light fixture. The control must also allow the fan and light to be operated separately, since the light will not be needed in daylight, for example. This means that the conventional two way light switch must be modified. The control should also preferably allow for different fan speeds, and possibly also different light intensities. Another requirement for the control is that it must not exceed a predetermined maximum power dissipation, and that the AC waveform arrive at the fan motor essentially undistorted to ensure relatively silent motor operation.
One approach to these problems in the past has been to provide several pull chain switches on the fan and light fixture itself to switch the power to the two devices on and off independently. However, since ceiling fans and lights are often installed on high ceilings and/or over furniture, access to the pull chain controls may be difficult or even hazardous. This control system is also awkward to operate and creates many situations where it is necessary to enter a room in darkness and attempt to find the correct pull chain to turn on the light.
Other approaches have involved modification of the standard wall located light switch. It is possible to control the fan and light separately from a wall location by rewiring the household circuit to run approximately six wires from the wall switch location to the ceiling outlet, but this is clearly undesirable because of the expense involved.
It is therefore desirable to control the fan and light operation, fan speed and light intensity separately and independently using the existing household wiring from a wall switch location. This is made difficult because only one side of the circuit is usually available at the wall location. Thus there is effectively no power available to operate a signalling device such as a radio transmitter, for example. It is difficult to provide the desired flexibility of independent operations from a single wall control switch, as can be seen from the prior art systems of this type.
One prior control system for selectively applying power to one or more of a group of devices, such as a ceiling fan and light, is described in U.S. Pat. No. 4,322,632 of Hart et al, in which the loads are selectively switched on in response to predetermined sequences of operations of the wall switch. Thus, the first load is switched on in response to a single switch closure, both loads are activated simultaneously by a successive switch closure, and a third switch closure activates the second load only. The repeated toggling of the switch is detected by transition detecting circuitry to operate the selected device. This involves complete interruption of power to the devices during signalling, which is undesirable. This sequence of switch operations is also clumsy and difficult to remember, and does not provide much flexibility in adding additional operations such as fan direction and speed controls and light intensity controls.
In U.S. Pat. No. 4,329,678 a different type of control system is shown in which control signals are generated which comprise delayed pulses superimposed on the AC power signal. Each electrical appliance is associated with a receiver which is responsive only to pulses having a predetermined phase value. By closing the appropriate switch of a multi-position switching assembly, a pulse having a predetermined phase value is produced which is detected by one or more of the receivers to operate the associated appliance. In this system both the control signal transmitters and the receivers are connected in parallel across the household power lines, requiring significant rewiring. Each appliance requires its own separate transmitter and receiver with a selected predetermined phase value for operation, significantly adding to the expense and complexity of the circuit. The circuit does not allow for different types of operation of a single appliance, nor does it allow two appliances to be operated either simultaneously or separately.
Another known ceiling fan and light control system is manufactured by Casablanca Fan Company under the name Inteli-Touch. This system is the subject of U.S. patent application Ser. No. 607,952 of Hart, filed May 7, 1984, and assigned to the Casablanca Fan Corp. In this system independent control of the fan and lights is provided without having to alter the wiring of a conventional home lighting circuit.
In the Casablanca system, two wall switches are used to operate the fan alone, the light alone, and the fan plus the light, in response to closure of either one or both of the two wall switches. Signals produced by closure of the switches comprise delayed pulses on the positive and negative going halves of each AC cycle, respectively, and pulses on both halves of the cycle. Detection circuitry detects the analog voltage level at a predetermined time interval after a zero crossing of the signal to determine whether a timing delay is present, and produces a control signal for operating a microprocessor when a delay is detected. This system therefore cannot tolerate phase shifting and is sensitive to line voltage variations.
In the Casablanca system special programs can be selected by operating the three switches in a specified sequence, with the resultant signal sequence detected by suitable circuitry to operate a microcomputer pre-programmed to initiate a predetermined sequence of events. This multiple switch operation must be completed within a predetermined time interval, i.e. within the first seven seconds after the power is turned on, and is difficult for the operator to remember without consulting product literature. Thus, for example, a security program to turn house lights on and off while no-one is at home is initiated by operating the light and fan switches in the following sequence: light, fan, light, fan. This is clearly relatively awkward and does not allow much potential for future additional programs to be added.